Various biochemical parameters were investigated in the gerbil cerebral cortex both during and after occlusion of the common carotid artery. Ischemia produced large changes in the energy metabolites, cyclic nucleotides and certain neurotransmitters, but had little or no effect on enzyme activities with the exception of protein kinase. From the data on the brain metabolites, there does not seem to be a major secondary change in energy metabolites for up to 6 hours of ischemia, but there is a gradual time-dependent change in the levels of putative neurotransmitters during the entire 6 hours of ischemia. Recovery from the ischemic insult was marked by a rapid restoration of energy metabolites, a short-term large increase in cyclic AMP, and a significant reduction in enzyme activities of Na ion, K ion-activated ATPase and adenylate cyclase. The results on enzyme and metabolites seem to indicate that the recovery process is dependent on the intensity of the ischemic insult and that recovery is more than a mere reversal of the ischemic-induced events. The pathological significance of these ischemia-related biochemical events are currently under investigation. BIBLIOGRAPHIC REFERENCES: Kobayashi, M., Lust, W.D. and Passonneau, J.V.: Concentrations of energy metabolites and cyclic nucleotides during and after bilateral ischemia in the gerbil cerebral cortex. J. Neurochem. 1977 (in press). Passonneau, J.V., Kobayashi, M. and Lust, W.D.: The effect of bilateral ischemia and recirculation on energy reserves and cyclic nucleotides in the cerebral cortex of gerbils. 1977 (in press).